JPH08340674A - Pushpull voltage converter and storoboscope power supply circuit - Google Patents

Abstract

PURPOSE: To provide a stroboscope power supply circuit with which charging can be finished in a short time and the waiting time of a stroboscope for the permission of light emission can be shortened and the power consumption can be saved to make more frequent stroboscopic emissions possible. CONSTITUTION: A pair of output transistors Q1 and Q2 are alternately turned ON by common control pulse signals. A current is applied to the half portion of the primary winding of a transformer T1 on a terminal P1 side and to the other half portion on a terminal P2 side alternately in the respective directions opposite to each other to reverse the magnetizing direction of the core of the transformer T1 alternately, so that the high power level voltage stepup can be performed with a high efficiency even if a small size transformer T1 is employed. In order to avoid the overlap of the ON-states of the output transistors Q1 and Q2, lines L1 and L2 with which the control transistor on this side are connected to the terminals on the other side are provided and a base current is not applied to this side until the other side is turned OFF.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generates an output of a voltage different from that of the primary power source on the secondary side of the transformer by turning on / off the direct current output of the primary power source with a transistor to perform push-pull operation of the transformer. The present invention relates to a push-pull voltage conversion circuit and a strobe power supply circuit capable of mounting this circuit.

[0002]

2. Description of the Related Art A strobe power supply circuit built in a camera forms a direct current voltage of several hundreds of volts from a battery output of several volts to charge an output capacitor and releases the electric power accumulated in the output capacitor at a stroke to discharge a discharge tube. Light up. FIG.
It is explanatory drawing of a structure of such a flash circuit. The output of the battery 31 (for example, 3V) of the primary power source is input to the booster circuit 33 via the switch 32. The step-up circuit 33 is a DC-type circuit that includes a step-up transformer and a switch transistor.
The DC converter forms a high-voltage DC output from the input low-voltage power and charges the output capacitor 34.

In the step-up circuit 33, a weak control pulse signal generated by the microcomputer circuit 37 is used to form a power pulse signal from the DC output of the battery 31. Then, the power pulse signal is input to the primary winding of the internal transformer, and the AC of several 100V extracted from the secondary winding is rectified to form a DC output. The DC output formed by the booster circuit 33 is stored in the output capacitor 34. The trigger circuit 35 excites discharge in the discharge tube 36 when a trigger signal synchronized with the shutter operation of the camera is input. The electric power accumulated in the output capacitor 34 for several seconds to several ten seconds is instantaneously (1 m
It is consumed in about 2 seconds.

When the step-up transformer of the step-up circuit 33 is composed of a simple transformer having a primary winding and a secondary winding each having two terminals and a DC power pulse signal is input to the primary winding, Since the current does not flow in the opposite direction even when it is turned on and off, the magnetization direction of the core of the transformer is only one direction, and the magnetic flux of the core is likely to be saturated even if the amplitude of the AC component is small. Therefore, the hysteresis loss of the core increases and the efficiency of the transformer decreases. Further, it is extremely difficult to reduce the cross-sectional area of the core and downsize the transformer.

Therefore, an intermediate terminal is provided on the primary winding of the transformer, and a trial production is performed in which power pulse signals in opposite directions are alternately supplied to two portions of the primary winding sandwiching the intermediate terminal. The core is alternately magnetized in both forward and reverse directions by using a power pulse signal formed by switching the direct current of the primary power source. The transformer is push-pulled using a pair of output transistors to alternately invert the magnetization direction of the core.

FIGS. 5 and 6 are explanatory views of an example of a push-pull voltage conversion circuit for performing a push-pull operation of a transformer by using an intermediate terminal. The circuits of FIGS. 5 and 6 are arranged between the transformer T1 in which the positive electrode (Vb) of the battery is connected to the intermediate tap P0 of the primary winding, and one terminal P1 of the primary winding and the negative electrode (ground) of the battery. NPN type output transistor Q
1, the other terminal P2 of the primary winding and the negative electrode of the battery (ground)
And the NPN type output transistor Q2 arranged in common, and by alternately turning on the output transistors Q1 and Q2, the magnetization direction of the core of the transformer T1 is alternately inverted.

In the circuit of FIG. 5, the base current of the output transistor Q1 is controlled to turn on the upper half current of the primary winding.
The control transistor Q3 that can be turned off and the control transistor Q5 that can control the base current of the output transistor Q2 to turn on / off the current in the lower half of the primary winding are both N.
It is a PN type, and both are collector-connected to the positive electrode (Vb) of the battery. Then, the control transistors Q3 and Q
A pair of control pulse signals having the same frequency and opposite phases are directly input to the base of the output transistor Q1, Q2.
Are alternately turned on. The pair of control pulse signals can independently adjust the phase and duty ratio.

On the other hand, in the circuit of FIG. 6, the control transistor Q3 for controlling the base current of the output transistor Q1 is set to N.
While using the PN type, the control transistor Q4 for controlling the base current of the output transistor Q2 is the PNP type,
The control transistors Q3 and Q4 are alternately turned on in the opposite phase of the common control pulse signal. Specifically, the control transistor Q3 is connected to the positive electrode (Vb) of the battery.
Is connected to the collector and the control transistor Q4 is connected to the emitter. When a common control pulse signal is input to the bases of the control transistors Q3 and Q4, the control transistor Q3 is turned on when the control pulse signal is at the H level phase.
However, at the opposite L level phase, the control transistor Q4 becomes O
N

Incidentally, the reason why the control pulse signal is indirectly input to the base of the control transistor Q4 via the capacitor C1 in FIG. 6 is that the input of the timing pulse is stopped as shown in FIG. This is because the PNP transistor Q3 is turned off and the output transistor Q2 is turned off while the level continues, so that no unnecessary current flows in the lower half of the primary winding.

[0010]

In the circuit shown in FIG. 6, the circuit shown in FIG.
As shown in, there is a problem that the period when the output transistor Q1 is ON and the period when the output transistor Q2 is ON partially overlap. Even after the output transistor Q1 is turned on and the potential of the terminal P1 is lowered, the output transistor Q2 continues to be turned on for a while and the potential of the terminal P2 is kept lowered. Further, even after the output transistor Q2 is turned on and the potential of the terminal P2 is lowered, the output transistor Q1 continues to be turned on for a while and the potential of the terminal P1 is kept lowered.

NPN type output transistors Q1 and Q2
Turns on at the same time as the base voltage rises,
It takes a few tens of seconds before the base voltage turns off after turning off.
A delay of 0n seconds to several microseconds occurs. Therefore, even if one of the output transistors Q1 and Q2 is turned on,
Keep ON for 0n seconds to several microseconds. Here, when current flows in one direction in the primary winding, power is consumed (accurately accumulated) in response to changes in the magnetic flux of the core, so impedance is formed in the primary winding and the current value is limited. Attached. However, when the output transistors Q1 and Q2 are turned on at the same time and a current flows in both directions in the primary winding, the magnetic fluxes of the cores cancel each other and the magnetic fluxes of the cores do not change, so that the impedance of the primary winding disappears and a large current flows. . At this time, the large-current power extracted from the battery 31 of FIG. 4 is consumed exclusively by the heat generation of the output transistors Q1 and Q2 and the heat generated by the internal resistance of the battery 31, so that the life of the battery 31 is impaired and the transistor 31 Q1 and Q2 may be destroyed.

On the other hand, in the circuit of FIG. 5, since the rising and falling timings of the pair of control pulse signals can be adjusted independently, after delaying the base voltage of the control transistor Q3 by several hundred nanoseconds to several microseconds. By raising the base voltage of the control transistor Q5,
It is possible to turn on the output transistor Q2 after surely turning off the output transistor Q1. Similarly, the output transistor Q1 is turned on after the output transistor Q2 is surely turned off.

However, it is necessary to form two independent control pulse signals by the microcomputer circuit 37 shown in FIG. 4 and input them to the booster circuit 33. In the normal microcomputer circuit 37, 2
It is difficult to independently adjust the duty ratio and the phase of the two control pulse signals of opposite phases. In particular, when the frequency of the control pulse signal is high (several kHz or more), the resolution of the microcomputer circuit 37 required for phase adjustment becomes finer because the pulse length is short. At 100 kHz, the pulse length is 5
It is necessary to have a performance capable of stably adjusting the phase in the unit of at least 100 nsec. In addition, a line connecting the microcomputer circuit 37 and the booster circuit 33, a relay terminal and a connector on the way are required twice as much.

For this reason, the load on the microcomputer circuit 37 and the wiring becomes large. In particular, in a strobe device with a built-in camera, the microcomputer circuit 37 is also used as a control circuit for the camera body function, and a special circuit needs to be added in order to precisely adjust the phase of the control pulse signal. . Also,
An increase in the number of lines and connector pins hinders the miniaturization of the camera and increases the manufacturing cost.

According to the present invention, even if a common control pulse signal is used, power pulses in opposite directions are not simultaneously supplied to the two parts sandwiching the intermediate tap, and the primary circuit is simple in spite of the simple circuit configuration. An object of the present invention is to provide a push-pull voltage conversion circuit that saves power of the power supply.

[0016]

According to a first aspect of the present invention, there is provided a push-pull voltage conversion circuit in which a transformer having a primary tap connected to one of the potentials of a primary power source, one terminal of the primary winding and the primary winding. A first output transistor arranged between the other potential of the power supply, a second output transistor arranged between the other terminal of the primary winding and the other terminal of the primary power supply, and a first output A first control transistor capable of controlling a base current of a transistor to turn on / off the current of the primary winding, and a first control transistor capable of controlling a base current of a second output transistor to turn on / off the current of the primary winding. Two control transistors, and by controlling the first control transistor and the second control transistor using a common control pulse signal, the first output transistor and the second output transistor are switched. In the push-pull voltage converter circuit for push-pull operation of the transformer is turned ON, the
A first control transistor is activated between the other terminal of the primary winding and the other potential of the primary power supply, and a second control transistor is activated between one terminal of the primary winding and the other potential of the primary power supply. It has a circuit configuration for operating the control transistor.

According to another aspect of the push-pull voltage conversion circuit of the present invention,
The push-pull voltage conversion circuit according to claim 1, wherein the positive terminal of the battery is connected to the intermediate terminal of the primary winding, and the first output transistor and the second output transistor are NPN transistors whose emitters are grounded, and the first control The transistor is an NP to which the pulse signal is directly input.
The second control transistor is composed of an N-transistor,
PNP to which the pulse signal is input via a capacitor
It is composed of transistors.

According to another aspect of the present invention, there is provided a strobe power supply circuit having a booster circuit for forming a high voltage from a DC voltage of a battery, which is built in a camera, wherein the booster circuit has an intermediate tap in a primary winding. The step-up transformer provided, a pair of output transistors that alternately supply power pulses in opposite directions to two portions sandwiching the intermediate tap of the primary winding, and ON / OFF of the pair of output transistors are controlled, respectively. A pair of control transistors, which controls the pair of control transistors by using a common control pulse signal formed by an oscillation circuit, and detects the turning-off of the output transistors of the other party, thereby A detection circuit for turning on is provided in each of the pair of control transistors.
According to a fourth aspect of the present invention, in the strobe power source circuit of the third aspect, the oscillation circuit is also used as a microcomputer circuit for controlling a main body function of the camera.

[0019]

In the push-pull voltage conversion circuit according to the first aspect, the first control transistor turns on the first output transistor by catching the timing when the second output transistor turns off. Therefore, even if the OFF of the second output transistor is delayed, the ON of the first output transistor is delayed by the delay. Similarly, the second control transistor catches the timing of turning off the first control transistor to turn on the second output transistor, and delays the turning on of the second output transistor by the delay even if the turning off of the first output transistor is delayed.

The output transistors are driven by a common control pulse signal via the respective control transistors, but the output transistors are not caused by the rising and falling of the control pulse signal but by the output transistors of the other side being turned off. It is turned on only when the result is detected. Therefore, even if the waveform, duty ratio, or frequency of the common input signal changes, the characteristics of transistors or other circuit elements change in the middle, or malicious noise invades, the first and second Only the result that two output transistors are turned on at the same time can be avoided.

According to another aspect of the push-pull voltage conversion circuit of the present invention, when the first output transistor is turned on, the voltage at one terminal of the primary winding drops, and a current flows from the intermediate terminal of the primary winding toward the one terminal. Flowing. When the second output transistor is turned on, the voltage at the other terminal of the primary winding drops, and a current flows from the intermediate terminal of the primary winding toward the other terminal. The direction of the magnetic flux generated in the core of the transformer by the current flowing from the intermediate terminal to one terminal is opposite to the direction of the magnetic flux generated in the core of the transformer by the current flowing from the intermediate terminal to the other terminal.

According to another aspect of the present invention, in the strobe power supply circuit, the pair of control transistors are alternately turned on by using the common control pulse signal output from the oscillation circuit, so that the pair of output transistors are alternately turned on and the transformer is turned on. Alternating power pulses are applied to the two parts of the primary winding that sandwich the center tap. As a result, magnetic flux in two directions, normal and reverse, are alternately generated in the core of the transformer, and voltage conversion with a high power level is possible. Further, for example, claim 1
As shown in FIG. 5, since the circuit configuration does not turn on the pair of output transistors at the same time, a wasteful current unrelated to the magnetization of the transformer, in other words, the voltage conversion of the transformer does not flow. In the strobe power supply circuit according to the fourth aspect, since the control pulse signal is output from the microcomputer circuit that controls the main body function of the camera, a dedicated oscillation circuit is unnecessary.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A strobe power supply circuit according to an embodiment will be described with reference to FIGS. 1, 2, 3, and 4. 1 is an explanatory diagram of a booster circuit, FIG. 2 is a diagram showing the timing of a transformer operation corresponding to FIG. 7, and FIG. 3 is a comparison diagram of circuit characteristics. In Figure 1,
(A) is a schematic block diagram corresponding to FIG. 5 and FIG. 6, (b)
Is a more specific circuit diagram. FIG. 4 shows a strobe power supply circuit of an embodiment mounted on a camera to drive strobe light emission.
The booster circuit 33 in the above circuit configuration is configured as shown in FIG. The microcomputer circuit 37 also serves as a circuit for controlling the mechanism of the camera body and calculating data. Microcomputer circuit 3
A clock pulse of 10 to several tens of kHz output from one of the terminals of 7 is input to the booster circuit 33 and used as a control pulse signal for driving the transformer.

In FIG. 1A, the transformer T1 is
The winding ratio of the primary winding to the secondary winding is 140, and the primary winding wound in one direction from the terminal P1 to the terminal P2 is taken out by half the number of windings to form the intermediate terminal P0. Intermediate terminal P0
Is connected to the positive electrode of a 3V battery whose negative electrode is grounded, and is an NPN type output transistor Q whose emitter is grounded.
When 1 is turned on to reduce the potential of the terminal P1, a current flows from the intermediate terminal P0 to the terminal P1 in the primary winding.
When the NPN type output transistor Q2 whose emitter is grounded is turned on to lower the potential of the terminal P2, the intermediate terminal P0
Current flows from the terminal to the terminal P2.

Since the current flowing from the intermediate terminal P0 to the terminal P1 and the current flowing from the intermediate terminal P0 to the terminal P2 are opposite in direction, the magnetization direction of the transformer T1 when the output transistor Q1 is turned on and the output transistor Q2 are turned on. The magnetization direction of the transformer T1 at the time of doing is opposite. Therefore, if the output transistors Q1 and Q2 are turned on alternately, the magnetic flux of the core of the transformer T1 repeatedly changes in one direction, 0, and the reverse direction, and the range within the saturation magnetic flux density of the core is utilized in both forward and reverse directions. Voltage conversion is possible. Output transistor Q
Due to the nature of semiconductors, 1 and Q2 turn on almost simultaneously with the rise of the base voltage (within several tens of nanoseconds), but do not turn off unless the base voltage falls for a while (several hundred nanoseconds to several microseconds). ).

A common control pulse signal is input to the bases of the control transistors Q3 and Q4. Similar to the circuit of FIG. 6, the control transistor-Q3 is an NPN type while the control transistor-Q4 is a PNP type, and the control transistors-Q3 and Q4 are alternately turned on by a common control pulse signal. Although the control pulse signal is input to the base of the control transistor Q4 through the capacitor C1, the capacitance of the capacitor C1 is selected such that charging / discharging by the base current or the like is not completed at the frequency of the control pulse signal. The base voltages of the control transistors-Q3 and Q4 rise at the same time and fall at the same time.

However, the collector of the control transistor-Q3 is not the power supply potential Vb of the circuit of FIG.
Since it is connected to the terminal P2 of the transformer T1 through the output transistor Q2 while the output transistor Q2 is turned on and a current flows between the terminals P0 and P2, even if the base voltage of the output transistor Q3 rises as shown in FIG. Since the terminal P2 is at the L level, the base current is not supplied from the emitter of the control transistor Q3 to the output transistor Q1. As shown in FIG. 2, the output transistor Q1 is first supplied with the base current and then turned on after the output transistor Q2 is turned off and the voltage of the terminal P2 starts to rise.

Similarly, since the emitter of the control transistor-Q4 is connected to the terminal P1 through the line L2, while the output transistor Q1 is ON and the current is flowing between the terminals P0-P1, it is as shown in FIG. As shown, even if the base voltage of the control transistor Q4 falls, the base current is not supplied from the collector of the control transistor Q4 to the output transistor Q2 because the terminal P1 is at the L level. As shown in FIG. 2, the output transistor Q2 is supplied with the base current and is turned on only after the output transistor Q1 is turned off and the voltage of the terminal P1 is increased. In other words, the output transistors Q1 and Q2 monitor each other's ON-OFF via the wirings L1 and L2, and the other side is open to some extent.
You cannot turn on yourself unless you do F. This allows
As shown in FIG. 7, the output transistors Q1 and Q2 are not turned on at the same time, and the terminals P0-P1 and the terminal P0 are not connected.
It is possible to avoid a situation in which current flows in the opposite direction at the same time between -P2.

When the control pulse signal is stopped and fixed at the L level, the base current of the control transistor Q4 and the like charges the capacitor C1 to raise the base voltage and the collector of the control transistor Q4 to the base of the output transistor Q2. Is stopped, and the output transistor Q2 is turned off. As a result, it is possible to avoid a situation where useless current flows between the terminals P0 and P2 of the primary winding when the control pulse signal is stopped. That is, the capacitor C1 permits turning on the output transistor Q2 while the control pulse signal continues, but prohibits turning on the output transistor Q2 when the control pulse signal stops.

FIG. 1B shows a more specific circuit configuration. The resistors connected between the emitters and the bases of the output transistors Q1 and Q2 and the control transistors Q3 and Q4 quickly neutralize the excess charge when the base voltage is inverted to stabilize the switch operation of each element. I am letting you. The resistance values of the other resistors are adjusted to optimize the operating range of each element. In particular, the resistance value between the base and collector of the control transistor Q4 is adjusted to a value that can surely stop the oscillation operation.

FIG. 3 shows changes in the charging time when several booster circuits, which are compared with the embodiment, are incorporated in the same strobe circuit of FIG. 4 as in the embodiment and light emission is repeated continuously. Comparative example J1 is the case of a booster circuit that simply uses a transformer without intermediate taps with the same boost ratio as that of the embodiment. Comparative example J2 is the booster circuit of FIG.
Comparative example J3 is the case of the booster circuit of FIG.

According to the strobe power supply circuit of the embodiment, since the magnetizing direction of the core of the transformer T1 is used in both forward and reverse directions, the portion of the core μ-H curve having a smaller hysteresis than that in the case of using it in one direction. (Linear part) can be used in full width. Therefore, high efficiency and high power level voltage conversion can be performed with a small transformer having a small core cross-sectional area. Therefore, as shown in FIG. 3, as compared with Comparative Example J1 in which the magnetization of the core is used in only one direction, in the Example, 1
The time required for one charge is significantly reduced, and the number of possible light emissions during the life of a battery having the same capacity is significantly increased. That is, the time to wait for the strobe to be charged is shortened, and the battery life is extended.

Further, since the control pulse signal supplied to the control transistors Q3 and Q4 is output from the microcomputer circuit 37 for the main body function of the camera, it is not necessary to provide an oscillator or waveform shaping circuit dedicated to the strobe power supply circuit. , The common control pulse signal is used, the microcomputer circuit 37 is compared with the comparative example J3 which uses two control pulse signals.
The number of signal ports for taking out signals from the device, the number of wirings, and the number of connector pins are small, and a circuit configuration for adjusting the phases of the two control pulse signals is also unnecessary. Therefore, the miniaturization of the strobe device facilitates the miniaturization of the camera. In addition, since the control transistors Q3 and Q4 have a circuit configuration that turns on after the other output transistors Q1 and Q2 start 0FF, the ON states of the output transistors Q1 and Q2 overlap and a wasteful current flows in the primary winding of the transformer T1. Does not flow. When the waveform of the control pulse signal is broken or the frequency is unstable, even if the semiconductor characteristics change due to temperature change, the control transistor Q3,
It does not affect that Q4 is turned on alternately. Therefore,
As shown in FIG. 3, the output transistors Q1 and Q2 are turned on.
Compared to the comparative example J2 in which the states overlap, efficiency is improved, power consumption is reduced, charging time is shortened, and the number of times of light emission is increased.

In this embodiment, the push-pull voltage conversion circuit of the present invention is applied to the strobe power supply circuit, but the application of the present invention is not limited to the strobe power supply circuit. For example,
It can be applied to high voltage generation circuit of corona discharge generator, low voltage large current generation circuit, etc., and can be applied not only to a camera built-in type but also to a single strobe device. Further, although the microcomputer circuit for controlling the camera is also used as the oscillation circuit of the control pulse signal, a dedicated oscillation circuit may be provided. The frequency and duty ratio of the control pulse signal may not be fixed and may be changed according to the boosting stage. In addition, the output terminal of the transformer, which has an intermediate terminal in the primary winding, is a current potential, and the output transistor is a grounded NPN transistor. A modification such as a PNP transistor connected to is also possible. However, in a configuration in which the output transistor is an NPN transistor and the emitter is connected to the transformer, the emitter potential rises at the moment when the output transistor is turned on, and a normal power pulse cannot be supplied to the transformer.

Although the control transistor is configured to operate via the output transistor between the transformer terminal and the ground potential, it is operated directly between the transformer terminal and the ground potential and further through one transistor. Alternatively, the base current of the output transistor may be controlled. The control transistor may be replaced with a circuit equivalent to the transistor, such as a Darlington connection circuit, or the bipolar transistor may be replaced with an FET. Various circuit configurations are possible in which the two control transistors are alternately operated by the common control pulse signal other than the embodiment. In any case, the circuit configuration may be such that it detects the OFF state of the output transistor of the other party and starts the ON state of the output transistor of its own. One example is a control transistor between the opposite terminal and the opposite potential of the intermediate terminal. Is a configuration of this embodiment in which a power pulse can be formed by the output transistor of the own side after the potential of the other side terminal starts to change.

[0036]

According to the push-pull voltage conversion circuit of the present invention, since the ON states of the first and second output transistors do not overlap, it is possible to prevent unnecessary current from flowing through the primary winding of the transformer. The transfer efficiency is improved and the power of the primary power source is saved. Since the core of the transformer is magnetized alternately in both forward and reverse directions, a small transformer is used to perform voltage conversion at high power level with high efficiency (low loss).
Can be performed by driving the pair of control transistors with a common control pulse signal, the circuit configuration is simplified, and the requirements for the phase and waveform of the control pulse signal (stability and adjustment resolution) are small.

According to the strobe power supply circuit of the present invention, the entire camera can be made compact and lightweight by downsizing the strobe power supply circuit itself, sharing a microcomputer circuit, and reducing the number of wires. Moreover, since the boosting is performed efficiently and at a high output level, the charging time is short and the battery life is long.
Specifically, the next stroboscopic photography can be executed in a short time after one stroboscopic photography, and the stroboscopic photography can be executed many times with one small battery. Further, by making the microcomputer circuit used for controlling the camera also serve as the oscillation circuit, there is no need to provide a dedicated oscillation circuit, and the frequency switching of the control pulse signal based on the convenience of the camera side can be easily executed. Become.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a booster circuit.

FIG. 2 is a diagram showing the timing of a transformer operation corresponding to FIG.

FIG. 3 is a comparison diagram of circuit characteristics.

FIG. 4 is an explanatory diagram of a strobe circuit configuration.

FIG. 5 is an explanatory diagram of a configuration of a comparative example of a booster circuit.

FIG. 6 is an explanatory diagram of a configuration of another comparative example of the booster circuit.

7 is an explanatory diagram of a problem in the comparative example of FIG.

[Description of sign]

 Q1, Q2 output transistor Q3 Q4 Q5 control transistor C1 capacitor T1 transformer P0 intermediate terminal P1, P2 terminal Vb power supply potential RC rectifier circuit L1, L2 line 31 battery 32 switch 33 booster circuit 34 output capacitor 35 trigger circuit 36 discharge tube

Claims (4)

[Claims] 1. A transformer (T1) in which one potential of a primary power source is connected to an intermediate tap (P0) of the primary winding, and one terminal (P1) of the primary winding and the other potential of the primary power source. The first output transistor (Q
1) and a second output transistor (Q) arranged between the other terminal (P2) of the primary winding and the other terminal of the primary power supply.
2), a first control transistor (Q3) capable of controlling the base current of the first output transistor (Q1) to turn ON / OFF the current of the primary winding, and a base current of the second output transistor (Q2). A second control transistor (Q4) capable of controlling ON / OFF of the current of the primary winding, and using a common control pulse signal, the first control transistor (Q3) and the second control transistor (Q4) ) Is controlled to alternately turn on the first output transistor (Q1) and the second output transistor (Q2) to perform the push-pull operation of the transformer (T1). The first control transistor (Q3) is operated between the other terminal (P2) and the other potential of the primary power source, and one terminal (P1) of the primary winding and the Push-pull voltage converter circuit, wherein the actuating the second control transistor (Q4) between the other potential of the next supply. 2. The push-pull voltage conversion circuit according to claim 1, wherein the positive terminal of the battery is connected to the intermediate terminal of the primary winding, and the first output transistor and the second output transistor are:
The first control transistor is an NPN transistor whose base is directly input to the pulse signal, and the second control transistor is a PNP transistor to which the pulse signal is input via a capacitor. A push-pull voltage conversion circuit comprising: 3. A strobe power supply circuit built in a camera, having a booster circuit for generating a high voltage from a DC voltage of a battery, wherein the booster circuit is provided with an intermediate tap (P0) in a primary winding for boosting. Transformer (T1) and a pair of output transistors (Q1, Q1) for alternately supplying power pulses in opposite directions to two parts sandwiching the intermediate tap (P0) of the primary winding.
2) and a pair of control transistors (Q3, Q4) for controlling ON / OFF of the pair of output transistors (Q1, Q2), respectively, and using a common control pulse signal formed by an oscillation circuit. The pair of control transistors (Q1, Q4) are controlled, and the detection circuits (L1, L2) for detecting the OFF state of the output transistor of the other side and starting the ON state of the output transistor of the other side are provided in the pair of control transistors (Q1, Q3,
A strobe power supply circuit provided in each of Q4). 4. The strobe power supply circuit according to claim 3, wherein the oscillation circuit is also used as a microcomputer circuit for controlling a main body function of the camera.